CHAPTER 1: OVERVIEW
SNAP PAC S-Series User’s Guide
11
Controller Redundancy
In this diagram, two S-series controllers are operating redundantly. One is the active controller, while the other
acts as a backup, ready to take over should the first one fail.
Controller redundancy requires PAC Project Professional R9.0 or newer and the Redundancy Option Kit, which
includes the arbiter and the redundant power switch in the diagram below. PAC Redundancy Manager, a
software utility for setting up and maintaining the system, is included in PAC Project Pro. The two controllers
you use must be exactly the same part number (for example, two SNAP-PAC-S2 controllers or two
SNAP-PAC-S1-W controllers).
As you can see, one advantage of an Opto 22 redundant system is that it uses standard PACs, standard cabling,
and standard I/O. Another advantage is that either controller can act as the active or backup controller; you
can switch their roles at any time for maintenance, for example. For detailed information on redundancy, see
the
SNAP PAC System Redundancy User’s Guide
(form 1831).
SNAP PAC I/O units
Ethernet switch
Redundant power switch
Arbiter
SNAP PAC controller
SNAP PAC controller
PC running PAC Project Professional
RS-485
Power control
Power
Ethernet crossover
cable connects the
PAC S2s on ENET2
RS-485
